1. Field of the Invention
The present invention relates to backlight keyboards and, particularly, to a backlight board used in a portable electronic device.
2. Description of Related Art
In a portable electronic device, a typical keyboard includes a plurality of keys, which display symbols, such as those found on typical alphanumeric keys, on their top surfaces. Moreover, this kind of keyboard is activated by depression of a key for identifying a particular symbol embedded on the top of the key. A problem with this kind of keyboard is that it is often difficult to discern the symbol appearing on the top of the key, under poor lighting conditions.
In order to solve the above problem, discrete light-emitting diodes (LEDs) are surface-mounted on a circuit board to provide illumination to a keypad. A light guide plate is arranged between the keypad and the circuit board for guiding light from one or more light sources on the circuit board to the proximity of the keypads.
However, the light guide plate not only guides light to each key, but also guides light to the area around keys. Accordingly, light from the LEDs not only illuminates each key but also illuminates other areas around keys. This wastes light and makes the symbols on the keys harder to discern/view.
Therefore, a backlight keyboard, which will efficiently use light from LEDs, is desired in order to overcome the above-described shortcomings.